Update: Converting Plastics to Energy Could Boost US Reserves

Although plastics make up only about 11% of all US municipal solid waste (MSW), many are actually more energy dense than coal. That means a lot of energy isn't being harvested from the more than 80% of already used material that goes to the landfill. Converting these non-recycled plastics (NRPs) into energy with existing technologies could reduce US coal consumption, as well as boost domestic energy reserves, says a new study by the Earth Engineering Center (EEC) of Columbia University. Of course, it would also reduce the carbon footprint of US waste management efforts.

Sponsored by the American Chemistry Council, the 2014 study updates an earlier one on the same topic we told you about back in 2011. The current report found that both recycling and energy recovery from all MSW increased between 2008 and 2011. During that time the recovery rate of plastics, including both recycling and energy recovery, grew from 14.3% to 17.3%. The study used 2011 data on waste management statistics from a Columbia University survey, plus studies conducted in several states characterizing MSW.

Although plastics make up only about 11% of all US municipal solid waste, many are actually more energy dense than coal. Converting these non-recycled plastics into energy with existing technologies could reduce US coal consumption, as well as boost domestic energy reserves. (Source: Earth Engineering Center/Columbia University)

The study's authors say that, if all NRPs in the US were converted into energy using modern plastics-to-oil facilities, they could produce enough gasoline to fuel nearly 9 million cars each year. There are several technologies for converting plastics to energy, such as mass burn, refuse-derived fuel, solid recovered fuel, gasification, and pyrolysis. We've told you about gasification and about plastics-to-oil. We've also given overviews of fuel recovery technologies for plastics and other waste here and here.

If all MSW, including plastics, that was sent to landfills in 2011 was converted to fuel using waste-to-energy (WTE) power plants, it would generate enough electricity to power 13.8 million US households, say the study's authors. That's about 12% of the current total number of homes. An additional 9.8 million homes could be heated just from the steam turbine exhaust of those WTE plants. That's already a practice in some northern European countries, such as Denmark.

Most organizations involved in waste management recognize that waste recycling and composting are more desirable than converting waste to energy. But that means the sources of the waste must be separable. When that's not the case, such as with non-recycled plastic, then the next-most desirable level on the hierarchy of sustainable waste management is energy recovery. (Source: Earth Engineering Center/Columbia University)

Converting all that waste to energy would also reduce landfill land use by 6,100 acres, about the size of 4,600 US football fields, as well as reduce greenhouse gas emissions equivalent to those from 23 million cars. If all the NRPs alone were source-separated and converted to crude oil or other types of fuel oil via pyrolysis, that would result in 136 million barrels of oil per year. Alternately, those diverted and converted plastics could produce enough electrical power each year for 5.7 million homes when used as fuel in dedicated power plants.

Some states already do a good job of diverting plastics from landfills by combining WTE conversion with recycling, the study's authors conclude. Those states include Connecticut, Maine, Massachusetts, Minnesota, and New Hampshire.

To answer your last question, Gorsky, "If this is a feasible approach to conversion of plastics into energy why hasn't somebody done something about it?" that's a very good question indeed. First, there are multiple methods used, as we mention. They all have different tradeoffs. Second, there's an infrastructure that has to be built for each one, since their products are different. Third, a market has to be developed for each one. I think you get the picture.Fact is, this already is being done, and that's part of what the study is tracking.

Gorsky, those are good questions, and are answered in several of the blogs we give links to. Generally, it all depends on the particular method used. For example, in this blog's second graphic, "source-separated materials" means sorted materials. Some plastics-to-energy methods require separated plastics and some don't. Check out the study, or our previous blogs, for more details.

On paper, this seems like a good idea waiting to happen. What the study doesn't say is what is involved in turning plastic into energy. Must it be sorted? How is that done. What energy inputs are required? Is there a net energy gain? If this is a feasible approach to converion of plastics into energy why hasn't somebody done something about it?

Encouraging article and a great idea. I did not realize how much energy is stored in the plastic objects that we throw away. I am also intrigued by the opportunity to reduce greenhouse gas emissions. While converting plastics to energy would reduce greenhouse gas emmisions from the plastics in landfills, would there be other, newer emissions generated from the resulting new conversion process? (I'm assuming there would still be a net reduction in greenhouse gas emissions).

It's good to know that recycling and waste-to-energy conversion increased since the last study 3 years ago. But what's disappointing is how small the increase was and how slowly the implementation of these efforts are progressing. The technology is already available, as we've reported. Establishing an infrastructure, though, takes a lot more time.

Many of the new adhesives we're featuring in this slideshow are for use in automotive and other transportation applications. The rest of these new products are for a wide variety of applications including aviation, aerospace, electrical motors, electronics, industrial, and semiconductors.

A Columbia University team working on molecular-scale nano-robots with moving parts has run into wear-and-tear issues. They've become the first team to observe in detail and quantify this process, and are devising coping strategies by observing how living cells prevent aging.

Many of the new materials on display at MD&M West were developed to be strong, tough replacements for metal parts in different kinds of medical equipment: IV poles, connectors for medical devices, medical device trays, and torque-applying instruments for orthopedic surgery. Others are made for close contact with patients.

Focus on Fundamentals consists of 45-minute on-line classes that cover a host of technologies. You learn without leaving the comfort of your desk. All classes are taught by subject-matter experts and all are archived. So if you can't attend live, attend at your convenience.